Effects of dexmedetomidine as an adjuvant in thoracic paravertebral block on EC50 of propofol for successful laryngeal mask insertion: a randomized controlled trial

Abstract

Background: Dexmedetomidine as an adjuvant can improve the duration and the quality of thoracic paravertebral block (TPVB); however, its quantitative effect on propofol infusion is unclear. This study aimed to investigate the effect of dexmedetomidine as an adjuvant in TPVB on the medium effective concentration (EC50) of propofol for successful laryngeal mask insertion.Methods: Sixty breast cancer patients who underwent elective modified radical mastectomy were enrolled and randomized at a 1:1 ratio into control group (Group C, n=30) or dexmedetomidine group (Group D, n=30). Ultrasound-guided T3 paravertebral block was performed before induction of anesthesia. In Group C, 0.5% ropivacaine 0.3 mL/kg was injected into T3 paravertebral space, while subjects in Group D received 0.5% ropivacaine 0.3 mL/kg with dexmedetomidine (1 μg/kg). Propofol target-controlled infusion (TCI) was performed, with an initial target effect-site concentration of 5 μg/mL determined for both groups.The laryngeal mask was inserted once the effect chamber achieved the target concentration. Subsequent target concentrations were adjusted by Dixon up-down sequential method, where dose modifications were performed by 0.5 mg/mL intervals, based on the success of the laryngeal mask insertion. Probit analysis was used to determine the propofol EC50. Mean arterial pressure (MAP), heart rate (HR), bispectral index (BIS) and application of atropine or ephedrine was recorded. Participants, TPVB giver, and data recorder were blinded to group assignment.Results: Propofol EC50 for successful laryngeal mask insertion were statistically significant, with 5.256 μg/mL (95% CI: 4.833, 5.738 μg/mL) in Group C and 3.172 μg/mL (95% CI: 2.701, 3.621 μg/mL) in Group D.Both groups displayed significantly lower MAP and HR, post propofol TCI (P<0.05). However, subjects in Group D exhibited lower MAP and HR levels compared to patients in Group C (P<0.05). Application of atropine (0% vs. 10%) and ephedrine (20.0% vs. 13.3%) were not significantly different between two groups.Conclusions: Dexmedetomidine, administered as an adjuvant in TPVB, can reduce the TCI concentration of propofol for successful laryngeal mask placement in females. The target concentration of propofol requires adjustment and close monitoring of hemodynamic changes, post induction is warranted.

Dexmedetomidine as an Adjuvant in Peripheral Nerve Block

“…However, the latest results of Zha et al 79 discovered that 0.5% ropivacaine combined with 1 μg/kg dexmedetomidine perineural application did not reduce the complications of hypotension and arrhythmia, despite producing a longer analgesic effect, reducing postoperative opioid consumption, and reducing the incidence of side effects, such as nausea and vomiting. Guo et al 80 studied the effect of dexmedetomidine as a PVB adjuvant on the effective concentration (EC 50 ) of propofol successfully placed in the laryngeal mask. The results demonstrated that 0.3 mL/kg of 0.5% ropivacaine combined with 1 μg/kg dexmedetomidine could reduce the TCI concentration of propofol, making it easier for female patients to place the laryngeal mask.…”